This invention is directed generally to liquid separation within liquid containers such as underground wells and, more particularly, to a method and apparatus for removing substantially immiscible liquids, such as hydrocarbons or pollutants from a collecting well which contains both water and such immiscible liquids.
There are various known techniques for removing immiscible liquids (hereinafter generally referred to as "liquids" or "liquid product") from containment apparatus. One such method is to employ a "cone of depression" technique. As stated in U.S. Pat. No. 4,746,423, the use of a "cone of depression" for collecting hydrocarbons from an underground well containing an overlying immiscible liquid, usually a hydro-carbon product, from an underlying, conductive, heavier liquid in a two liquid body is well established. The technique requires a depression pump located at or near the bottom of a well to remove water in large enough quantities to actually lower the water table locally, and thereby cause underground liquids to drain toward the region in which the table is depressed. The lighter liquid products then collect within the well along with the water and typically as the water is pumped out by the depression pump, a skim pump located higher in the well, in the region atop the collected water where the lighter fluid products collect, is used to pump out the contaminants. Several examples of this technique and other removal schemes may be found in the patents listed below.
U.S. Pat. No. 4,273,650 to Solomon teaches a system using a cone of depression technique which employs a submergible, drawn down, electrically powered pump submerged at the bottom of a well. A water discharge control including the pump and the pump switch controls the flow of water from the well to establish and maintain by gravity flow a predetermined liquid level at a spaced distance below the static water table. In this way, a cone of depression is established. A combined pollutant pump and sensor apparatus including an electrically powered pollutant pump, a pump switch and sensors responsive to pollutant level to actuate the pump switch are supported in the well at the level of the apex of the cone of depression. The Solomon apparatus also includes sensors for sensing a low level water/pollutant interface and energizing the pollutant pump to pump pollutant into a tank while permitting the water/pollution interface to rise and also for sensing a high level water/pollutant interface and de-energizing the pollutant pump upon sensing the high level water/pollutant interface.
U.S. Pat. No. 4,469,170 to Farmer, Jr. teaches a skimmer which is designed to float in the two-liquid body contained in the well. The Farmer, Jr. skimming apparatus requires a float and, apparently, also requires a depression pump.
U.S. Pat. No. 4,746,423 to Moyer discloses a two pump skimmer system for recovery of lighter-than-water hydrocarbons from water wells. The pumps are located in individual chambers which are interconnected with the water chamber below the hydrocarbon chamber and with limited one-way flow into the water chamber. Both pumps are independently controlled by sensors in the upper chamber to assure that each pumps only the proper liquid.
U.S. Pat. No. 4,766,957 to McIntyre discloses a method and apparatus for gravitationally separating hydrocarbons and water discharged from a subterranean well. McIntyre teaches that a mixture of hydrocarbons and water flows into the interior of a well casing through perforations disposed adjacent the production zone. The water flows downwardly or is forcibly pumped downwardly to the water absorbing formation and is absorbed in such formation.
U.S. Pat. No. 4,770,243 to Fouillout, et al. shows a microprocessor controlled system for separating water from hydrocarbons. The Fouillout device is directed to the field of the production of petroleum from deposits in which water is mixed with hydrocarbons, and not to the skimming of contaminant hydrocarbons from a water producing well. Separation of the water from the hydrocarbons is accomplished at the bottom of the well in a packer.
U.S. Pat. No. 4,761,225 to Breslin discloses an apparatus for controlling the removal of liquid hydrocarbons from groundwater in a perforated well casing consisting of a plurality of pump chambers and a control system which is powered by compressed air.
The present invention has advantages over the prior art in that, it is believed that for the first time, it provides a highly dynamic, automatic microprocessor-controlled system which has a programmable operation capable of using a single sensor in combination with a float sensor to control both a skim pump and a depression pump, thereby promoting cooperation between the two pumps to result in hydrocarbon removal. The invention provides a microprocessor based controller for a "cone of depression" type removal system which heretofore has not been found in the prior art. In yet another aspect of the invention, a method and apparatus is provided to remove floating liquids using only an interface sensor and a microprocessor controlled skim pump, without employing a depression pump to create a cone of depression.